1. Field of the Invention
The present invention concerns a method to generate MR angiography images, as well as a correspondingly designed magnetic resonance apparatus.
2. Description of the Prior Art
As is known, the generation of MR angiography images takes place either by injecting a contrast agent before the acquisition of the MR data, or injection of a contrast agent is foregone. In methods in which the injection of the contrast agent is foregone, the data acquisition is conventionally assisted by activation of an EKG (electrocardiogram). Using this EKG activation, in the data acquisition it is known whether the corresponding MR data are acquired during the arterial phase or during the venous phase of the heart. The arterial phase is the phase in which the heart pumps the blood in the arteries. The venous phase is the phase in which the blood is directed back to the heart via the veins.
It is known that a series of problems results from the detection and post-processing of the EKG signal. For example, injection of the RF signals (generated by the magnetic resonance system) into the EKG hardware lead to false activation signals by the EKG hardware. Moreover, a variable heart beat (arrhythmia) of the patient leads to problems in the data acquisition because, in this case, the point in time of the data acquisition is frequently associated with the wrong phase. Furthermore, a delay time must be allowed dependent on the distance that the blood vessels to be examined are from the heart. Finally, EKG activation signals and the corresponding arterial or venous phase have only slight correlations at distal segments of a vascular tree, such that the EKG activation signals do not optimally coincide with the respective phases given existing deviations of the physiology of the patient from the norm.